Discoveries in the field of physics dealing with semiconductor devices has lead to a considerable miniaturization of electronic components and circuitry. Unsuccessful attempts have been made to miniaturize strip-line directional couplers so that they are compatible with other improved electronic components and circuitry. Directional couplers require a rather long package since the coupling between an input line and an output line is usually required over a fairly long distance. In U.S. Pat. No. 3,460,069 an improvement in packaging of directional couplers is set forth in which the coupling lines have a path which winds back and forth between the input and output of the board in a serpentine manner to provide a smaller package. It has been subsequently found that placing the serpentine wound circuit lines closer to further miniaturize the package has caused adverse electrical effects. Actually, the closer spacing of the electrical lines with respect to one another when wound in a serpentine fashion caused a curtailing of the coupling therebetween in adjacent lines. These adjacent lines have electrical signals travelling therethrough in opposite directions and accordingly the coupling tended to detract and hence diminish the electrical characteristics of the coupler.
As is known, the strip-line directional coupler is a device wherein two parallel adjacent printed circuit strip-lines sandwiched between two ground planes are inductively and capacitively coupled so that the edges of a first pulse, of fast rise and fall time characteristics, propagating along one line, produce a positive pulse and a negative pulse in the other line. The lines are back coupled or directional in that the thus produced pulses propagate along the second line in a direction opposite to the direction in which the first pulse propagates along the first line.
The energy transferred between the coupling segments of the two element directional coupler is effected by the various physical characteristics of the directional coupler such as the length, width and distance between the coupling segments. Accordingly, the long coupling element lengths needed to obtain a good energy transfer between the segments of the coupler introduces obvious disadvantages in packaging the two-element directional coupler.
Accordingly, it is an object of the present invention to provide a strip-line directional coupler package having a flat small volumetric size without a consequent reduction in electrical operation.
It is another object of the present invention to provide a strip-line directional coupler package having improved electrical characteristics which enable a reduction in volumetric size.
It is another object of the present invention to provide a strip-line directional coupler in which the electrical characteristics are enhanced while the volumetric size is reduced.
It is a further object of the present invention to provide a strip-line directional coupler package in which the dielectric material and ground planes in a circuit card are also utilized as part of the directional coupler.